Ahmad Kamal Ariffin Mohd Ihsan

The peridynamic model of viscoelastic creep and recovery

Purpose – The purpose of this paper is to establish a peridynamic method in predicting viscoelastic creep behaviour with recovery stage and to find the suitable numerical parameters of peridynamic method. Design/methodology/approach – A rheological viscoelastic creep constitutive equation including recovery and an elastic peridynamic equation (with integral basis) are examined and used. The elasticity equation within the peridynamic equation is replaced by the viscoelastic equation. A new peridynamic method with two time parameters, i.e. numerical time and viscoelastic real time is designed. The two parameters of peridynamic method, horizon radius and number of nodes per unit volume are studied to get their optimal values. In validating this peridynamic method, comparisons are made between numerical and analytical result and between numerical and experimental data. Findings – The new peridynamic method for viscoelastic creep behaviour is approved by the good matching in numerical-analytical data compariso...

Material property characterisation method using vibro-acoustic signals

Material play an important role in engineering design and the characterisation of material property has become an essential requirement for their successful application as structural elements. In this paper, the development of material property characterisation method has been presented. Impulsive excitation test has been performed on rectangular bars (medium carbon steel S50C, cast iron FCD 500, stainless steel AISI 304and brass). The transient vibro-acoustic signals generated during the excitation test have been captured using data acquisition system consist of accelerometer-microphone combination. A new method for reducing the noise components from the recorded signals is introduced by an extensive process of a new Z-stem filtering technique. The filtered signals have been analysed using an alternative statistical method known as Integrated Kurtosis-based Algorithm for Z-notch filter (I-kazTM) to determine the pattern of the signal and to estimate the significance differences among those materials. The representation of the experimental curves obtained by the determination of I-kaz coefficient, Z∞ for various impact forces and materials revealed that the results are statistically significant and can be successfully used for determining the correlation between the curves and material property. Implications of this research to material property characterisation will be discussed.

Characterisation of the Sound and Vibration Signal of Impact Testing on Automotive Component Materials

Dynamic response of automotive component materials which are carbon steel S50C and cast ironon its sound and vibration characteristichas been studied. This paper shows that I-kaz analysis method can be applied to characterise this dynamic behavior problem. In the present work, an excitation has been performed by an impact hammer at the center of a rectangular bar specimen instrumented with accelerometer and microphone to obtain sound and vibration time-histories. From the experimental results, it was found that the recorded sound and vibration signal has a transient characteristic with high oscillation. Frequency spectrum analysis shows that impact testing on any material will generate its own characteristic of frequency peak and constantboth for sound and vibration signal. From I-kaz analysis method, it can be concluded that I-kaz coefficient, for sound signal is proportional to the modulus of elasticity, density and Poissons ratio. It is also shown that for vibration signal is inversely proportional to these mechanical properties.Data scattering representation supported this pattern of .

Subsurface Deformation of Worn Al-Cu and Al-Mg Alloys

This paper investigates the subsurface deformation of two types of aluminium alloys with differing nature; A2124 (precipitation-hardened) and A5056 (work-hardened), sliding against an M2 tool steel slider. With block-on-ring configuration, the wear test was carried out at different loads ranging from 23 - 140N, in a dry sliding condition. Detailed secondary electron microscopy (SEM) performed on the longitudinal cross sections of the worn alloys indicates that the subsurface deformed layer beneath the worn surfaces is composed of a number of distinct layers like the mechanically mixed layer (MML), the shear deformed and bulk layers with increased hardness as the surface was approached. Deformation below the MML followed the expected behaviour of an exponential decay of strain with depth. In contrast to other studies in the literature, a linear relationship between depth of deformation and specific wear rate was not found for both alloys. This was believed to a result of the MML, which occupied a great proportion of the total depth of deformation. The relationship between the characteristics of the MMLs especially on the work hardening as a function of alloy type is also discussed.