Indian Journal of

Engineering & Materials Sciences

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VOLUME 17

NUMBER 1

FEBRUARY 2010

CODEN : IEMSEW

ISSN : 0971-4588

 

CONTENTS

 

Engineering

 

Improvement in part-load performance of a manifold injected spark ignition engine an experimental investigation

 

7

H R Purushothama, J M Mallikarjuna & V Ganesan

 

 

 

Plastic deformation regularity of tailor-welded tube hydroforming

13

Guannan Chu & Feng Li

 

 

 

Comparative study on the suitability of feature extraction techniques for tungsten inclusion and hotspot detection from weld thermographs for on-line weld monitoring

 

 

20

N M Nandhitha, N Manoharan , B Sheela Rani, B Venkatraman,

 

P Kalyanasundaram & Baldev Raj

 

 

 

Effects of SNF and LS superplasticizer on cement paste using electrical measurement

 

27

Xiaohui Zeng & Tongbo Sui

 

 

 

Design of low phase noise InGaP/GaAs HBT-based differential Colpitts VCOs for interference cancellation system

 

34

Bhanu Shrestha & Nam-Young Kim

 

 

 

Materials Science

 

Failure response of single bolted composite joints under various preload

39

Faruk Sen, Onur Sayman, Resat Ozcan & Ramazan Siyahkoc

 

 

 

Investigation into the densification of AISI304 parts fabricated by hybrid powder metallurgy techniques

 

49

Z L Lu, J H Liu, Y S Shi & D C Li

 

 

 

Densification behaviour of Al-Pb alloys A study of effect of certain process parameters

 

56

Ch V S H S R Sastry & G Ranga Janardhana

 

 

 

 

 

 

 

Mechanoluminescence technique for real-time monitoring of cracks produced during application of loads on crystals

 

61

B P Chandra, S K Mahobia, S K Nema, P Jha, R K Kuraria & S R Kuraria

 

 

 

Metallurgical analysis of burst tested aluminium alloy AA 2219 miniature assembly

67

Abhay K Jha, V Diwakar & K Sreekumar

 

 

 

 

 

 

 

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 17, February 2010, pp. 7-12

 

 

Improvement in part-load performance of a manifold injected spark ignition engine an experimental investigation

H R Purushothama, J M Mallikarjuna & V Ganesan

 

This paper deals with the experimental investigations carried out on a single-cylinder, four-stroke, manifold injected spark ignition engine to improve the part-load performance and emission characteristics by modulating the inlet valve closure timing (IVCT) and clearance volume (CV). The IVCT is delayed in order to reduce the volumetric efficiency of the engine with full throttle operation which in turn reduces the brake power output so that engine can be operated at part-load. In addition, the CV is also reduced with respect to IVCT to maintain the effective compression ratio (ECR) of the engine. These things change the geometric expansion ratio (GER) and ECR of the engine along with reduced pumping losses to increase the brake thermal efficiency and reduce the exhaust emissions at part-loads. In order to vary the part-load brake power output, a suitable combination of the IVCT and CV is used which in turn vary the GER/ECR ratio of the engine. In this study, experiments are carried out for the different GER/ECR ratios varying from 1.25 to 2 with two ECRs of 7 and 8 at a constant engine speed of 1500 rev/min. From the results, it is found that for GER/ECR ratio of 1.5 with ECR of 8 and 7, the improvement in brake thermal efficiency is about 3.5 and 6.6%, the reduction in unburned hydrocarbon emissions is about 25 and 22.5% and the reduction in nitric oxides emissions is about 51 and 52% respectively compared to conventional engine at the corresponding brake power outputs.

Keywords: Extended expansion engine, Manifold injection, Spark-ignition engine, Part-load performance

 

Indian Journal of Engineering & Materials Sciences

Vol. 17, February 2010, pp. 13-19

 

Plastic deformation regularity of tailor-welded tube hydroforming

Guannan Chu & Feng Li

To reveal the deformation characteristics and influence of dissimilar thickness on hydro-bugling of tailor-welded tube (TWT), FEA, experiments and mechanics analysis are conducted. The effects of length ratio, weld-seam movement and work-hardening on deformation compatibility are analyzed. It indicates that the plastic deformation occurs first at the middle zone of the thinner tube, and then extends to the thicker tube crossing the weld-seam. The expansion occurring on the two parts with dissimilar thickness is non-uniform, higher the length ratio and higher the deformation compatibility. Stress-strain analysis reveals that though the whole TWT suffers biaxial tensile stresses and the biaxial elongation occurs in the thinner tube, axial compressive strain occurs in the thicker tube. It is concluded that the mechanism for improving the deformation compatibility is to induce the deformation in the thicker tube by enhancing the bulging pressure needed for the thinner tube through changing the stress state of the thinner tube and flowing stress. Weld-seam movement happens during tailor-welded tube hydroforming, which induces uneven distribution of axial strain and thinning ratio in the TWT.

Keywords: Tailor-welded tube, Dissimilar thickness, Weld-seam movement, Thinning ratio

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 17, February 2010, pp. 20-26

 

 

Comparative study on the suitability of feature extraction techniques for tungsten inclusion and hotspot detection from weld thermographs for on-line weld monitoring

N M Nandhitha, N Manoharan, B Sheela Rani, B Venkatraman, P Kalyanasundaram & Baldev Raj

 

Welding is the most commonly used technique for joining metals in industries. In spite of various technological advances defects do occur in welds. Post non-destructive testing (NDT) techniques assess the quality of weld after completion of welding process. Monitoring and controlling weld parameters during welding can avoid the defect or if the defect is already intolerable the welding process can be stopped there to save time and money. It is thus necessary to develop an automated on-line welding system to make the correct decision. Weld thermographs are acquired on-line with IR camera. Effective feature extraction algorithms are to be developed to isolate and quantify the defect features from thermographs. This paper compares the effectiveness and suitability of three different feature extraction algorithms namely discontinuity based detection (conventional), region growing and Euclidean distance based color image segmentation developed for on-line monitoring and control. Tungsten inclusion and different depths of penetration thermographs are the database considered for defect feature extraction. Online weld monitoring necessitates a standardized feature extraction technique that works well irrespective of the size and shape of defect. Hence, comparison is based on the accuracy of the results, parameter independency and image independency. It is found that feature extraction by Euclidean distance based segmentation is best suited for on-line weld monitoring as it is parameter independent and can be standardized for a defect.

Keywords: Thermographs, Depths of penetration, Tungsten inclusion, Edge detection, Region growing, Euclidean distance, Feature vectors

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 17, February 2010, pp. 27-33

 

 

Effects of SNF and LS superplasticizer on cement paste using
electrical measurement

Xiaohui Zeng & Tongbo Sui

 

A non-contact electrical resistivity measurement is used to study the effects of sulfonated naphthalene formaldehyde condensates (SNF) and lignosulphonate (LS) superplasticizers on cement paste. Other experiments like fluidity test and test of the amount of superplasticizer adsorbed on cement particles are also carried out. Results show that SNF superplasticizer has different effects on the resistivity of cement pastes comparing with LS superplasticizer. The plot of initial resistivity versus SNF dosage can be divided into 4 zones. Each zone reflects the characteristics of SNF as a superplasticizer of cement paste, respectively. The curves of the resistivity developing with time; ρ(t), and their derivatives; dρ(t)/dt(t), have distinct changes when the dosages of SNF and LS superplasticizer are high. Electrical method is potentially a very useful method in concrete designing.

Keywords: Cement, Electrical resistivity, Superplasticizer, Fluidity, Adsorption, Dissolution

 

Indian Journal of Engineering & Materials Sciences

Vol. 17, February 2010, pp. 34-38

 

Design of low phase noise InGaP/GaAs HBT-based differential Colpitts VCOs for interference cancellation system

Bhanu Shrestha & Nam-Young Kim

 

This paper presents design, fabrication and characterization of two differential Colpitts voltage controlled oscillator (VCOs) - cross-coupled VCO (CC-VCO) and double cross-coupled VCO (DC-VCO) - in InGaP/GaAs HBT technology. Their main parameters like the oscillation frequency, output power and phase noise performance are measured and compared with other recently published studies. In the cores of two VCOs, two switching transistors are introduced to steer the core bias current to save power. An LC tank with higher inductor quality factor (Q) is used to generate oscillation frequency. The differential CC-VCO exhibited a superior phase noise characteristics of-130.12 dBc/Hz at 1 MHz from the carrier frequency (1.566 GHz) when supplied with a control voltage of 0 volt. In the same way, the differential DC-VCO achieved -134.58 dBc/Hz at 1 MHz from the carrier frequency (1.630 GHz) with the same control voltage. Two pairs of on-chip base collector (BC) diodes are used in the tank circuit to increase the VCO tuning range. It is concluded that the faster switching action of InGaP/GaAs HBT transistors exhibited the excellent phase noise characteristics.

Keywords: Differential VCO, InGaP/GaAs HBT VCO, MMIC VCO, Voltage controlled oscillator, Differential Colpitts VCO, Low phase noise VCO, Colpitts oscillator

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 17, February 2010, pp. 39-48

 

Failure response of single bolted composite joints under various preload

Faruk Sen, Onur Sayman, Resat Ozcan & Ramazan Siyahkoc

 

In this study, an experimental failure analysis is performed to calculate bearing strength of single bolted joints in laminated composites reinforced unidirectional glass fibers. The main goal of this study is to determine the failure behaviour of bolted composite joints under various preload moments as 0, 2.5 and 5 Nm. Furthermore, two different geometrical parameters that are the edge distance-to-hole diameter ratio (E/D) and plate width-to-hole diameter ratio (W/D) are investigated. For that reason, E/D and W/D ratios are selected from 1 to 5 and from 2 to 5, respectively. Besides, the effect of orientation angle of laminated plates is considered. Therefore, four different ply orientations are selected as [30o]4, [45o]4, [60o]4 and [90o]4. The experimental results show that the magnitudes of bearing strengths in single bolted composite joints are strictly influenced from increasing value of applied preload moments, changing of W/D and E/D ratios and also ply orientations.

Keywords: Bearing strength, Failure analysis, Fiber reinforced composites, Laminated plates, Bolted joints

 

Indian Journal of Engineering & Materials Sciences

Vol. 17, February 2010, pp. 49-55

 

Investigation into the densification of AISI304 parts fabricated by hybrid powder metallurgy techniques

Z L Lu, J H Liu, Y S Shi & D C Li

 

Complex and high-performance parts of metal and ceramics can be fabricated by selective laser sintering/isostatic pressing (SLS/IP), in which cold isostatic pressing (CIPing) is introduced into SLS followed by high sintering (HSing) and hot isostatic pressing (HIPing). In this paper, the mechanisms of action of CIPing pressure and HSing temperature on relative densities of AISI304 parts fabricated by SLS/IP are respectively investigated. Based on the liquid sintering theory, the effects of trace FeB on their relative densities, metallurgical structures and mechanical performances are likewise analyzed. Results show that there is a minimal threshold of CIPing pressure for AISI304 parts in the process of SLS/IP, which is about 400 MPa. Their relative densities approximates certain value with an increase of HSing temperature from 1250C to 1350C, which are improved while their mechanical performances worsen with an increase of FeB content from 0.5% to 5.0%, and their metallurgical structures consist of eutectic (a-Fe, Fe2B) and (Ni,Ni3B) besides austenite (Fe,Cr,Ni,C). Although their strengths are better when FeB content is 0.5wt%, their elongation percentages are lower, which is only about 8%.

Keywords: Powder metallurgy, Selective laser sintering, Isostatic pressing, Relative density

 

Indian Journal of Engineering & Materials Sciences

Vol. 17, February 2010, pp. 56-60

 

Densification behaviour of Al-Pb alloys A study of effect
of certain process parameters

ChV S H S R Sastry & G Ranga Janardhana

 

The recent research into the alternate sliding bearing materials unequivocally point to the beneficial role of lead in aluminum. But, these alloys offer a manufacturing challenge, due to wide immiscibility gap. For sliding bearing applications, controlled porosity (size, distribution and nature) is an important consideration, as it influences the tribological performance through mechanical properties and spreading of lead in aluminum matrix. In the present investigation, the effects of alloy composition, ball to charge ratio and mixing/milling route on densification behaviour of Al-Pb alloys processed through conventional ball milling and attrition milling routes, using XRD, SEM and compressibility test are studied. The resulting morphological changes of powder complexes are examined, on five compositions of alloys to determine compaction response. The study concludes that attrition milling is an effective method for densification of experimental alloys.

Keywords: Al-Pb alloys, Powder metallurgy, Compressibility test, Densification behaviour

 

 

 

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 17, February 2010, pp. 61-66

 

Mechanoluminescence technique for real-time monitoring of cracks produced during application of loads on crystals

B P Chandra, S K Mahobia, S K Nema, P Jha, R K Kuraria & S R Kuraria

 

When a load is applied on to a crystal, then the fracto- mechanoluminescence (ML) emission takes place in the form of light pulses. The number of ML pulses and the time duration tc for the appearance of ML increase with increasing value of the load and the average ML intensity from a single ML pulse decreases with increasing value of the load. For a given value of the applied pressure, the total number NT of ML pulses, the total ML intensity IT and the time duration tc of ML emission increase with increasing size of the crystals. As the total ML intensity is directly related to the area of newly created surfaces, the pressure dependence of the total ML intensity indicates that initially the total area of newly created surfaces increases with increasing value of the applied load and later on it tends to attain a saturation value for higher values of the applied load. As the strain rate is maximum at a particular time after the application of load on to a crystal, the rate of the emission of ML pulses is maximum at a particular time after the application of load on to the crystals. The dependence of NT, IT, and tc on the applied pressure Po follows the following expressions, respectively

 

NT = Mo Vy [1 exp{δc (Po Pf)}]

IT = D b Mo V [1 exp{δc (Po Pf)}]

and,

where V is volume of crystal, y is an exponent, δc =1/Pc, Pc is the critical pressure, Pf is the fracture stress, Mo, D, b, and α are constants. A good agreement is found between the theoretical and experimental results.

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 17, February 2010, pp. 67-71

 

Metallurgical analysis of burst tested aluminium alloy AA 2219 miniature assembly

Abhay K Jha, V Diwakar & K Sreekumar

 

A miniature assembly fabricated from aluminium alloy AA 2219 forging and 2.0 mm thick sheets is subjected to burst test using a pressure cartridge at very high strain rate of loading. The microstructural features associated with deformation at high rate of loading using explosive energy is analyzed by optical and scanning electron microscopy (SEM). The microstructures consisted of adiabatic shear bands formed in an extremely short time by the combined effects of the highly localized shear deformation and the high temperature rise that occurred within the shear bands. Scanning electron microscopy revealed features of melting within the adiabatic shear band. This paper highlights the details of experiment carried out and the salient observations at microscopic level on the fracture surfaces taken from the test article.

Keywords: Adiabatic shear band, Deformation under high strain rate, Fracture, Burst test, AA 2219