K. Sankaranarayanasamy

Whole Body Vibration Analysis for Drivers of Suspended Cabin Tractor Semitrailer

This work has been conducted to find out the health risk associated with driving suspended cabin tractor semitrailer. Suspended cabin tractor semitrailer drivers are exposed to whole body vibration during their work. Some drivers suffer from low back pain caused by vibration. However, due to the lack of investigations there is no evidence of relation between the whole body vibration from the means of conveyance and low back pain. The practical significance of applying suspended cabin type of tractor semitrailer was tested at different road conditions as well as in both loaded and unloaded conditions at different speeds for comfortable driver seat interface (x—longitudinal, y—transverse, and z—vertical axes). Average running root mean squared weighted accelerations for suspended cabin tractor semitrailer were between 0.5624 and 1.4368 m/s2 at the driver seat interface in the translational axes. The acceleration suspended cabin tractor semitrailer drivers are prove to exceed the upper exposure limit of 8-h work day as outlined in ISO 2631 when they work continuously.

Design and manufacturing tolerances optimisation with quality loss functions

The competition in the current world market has forced the manufacturers to produce products with low cost and high quality. Production of high quality products at low cost requires the concurrent optimisation of design and manufacturing tolerances along with quality loss. Tolerance allocation is a design tool for minimising over-all cost of manufacturing, while meeting target levels for quality. Since, in traditional method, the allocation of tolerances is based on designers own experience, it may significantly affect a products quality and the resulting manufacturing costs. Hence, in this work, the tolerance allocation problem is formulated as a non-linear integer model by considering both the design and manufacturing tolerances so as to minimise the manufacturing cost and quality loss. Genetic algorithm is employed to solve the model and an example is presented to illustrate the methodology. Results are compared with conventional techniques and the performances are analysed.

Experimental Evaluation of Whole Body Vibration Exposure from Tracked Excavators with Hydraulic Breaker Attachment in Rock Breaking Operations

Ever expanding technological growth has led to an increase in the use of tracked excavators for construction, demolition, material handling, rock breaking etc. Excavator operators are exposed to a variety of risk factors that may lead to health problems. A major health hazard among operators is whole-body vibration. Human response to vibration is very complex and nonlinear. Whole Body Vibration in the range of 2 to 30 Hz corresponds to most of the resonant responses of various organs and parts of the human body. The objective of this paper is to assess whole body vibration for the tracked excavator with hydraulic breaker. The job safety analysis conducted through questionnaires for different industrial vehicle operators revealed the presence of a health risk among the operators in rock breaking machinery. To quantify the level of vibration, field tests are performed on four tracked excavators with hydraulic breaker attachments in two different work locations. Accelerometer, a real-time signal conditioning / processing and PULSE data acquisition software are used for vibration measurement. The frequency of vibration exposure is observed to be between 6.8 and 12 Hz. Acceleration levels measured were in the range of 0.87 −2.2 m/s2 for a tracked excavator operator with breaker. The total vibration exposure calculated was between 0.621 and 1.932 m/s2. The vibration dose value recorded was 17.6 −62.72 m/s1.75. Whole body vibration exposure of the breaker operator was much higher and lies beyond the upper limit as given in ISO 2631–1. The ranges of vibration parameters measured were concomitant with frequent lower back pain, other muscular-skeletal injuries like leg pain etc which are prevalent among these operators.

Finite Element analysis of heat distribution in laser beam welding of AISI 304 Stainless Steel sheet

Laser beam welding of AISI 304 austenitic stainless steel is performed by varying beam power, welding speed, beam angle and gas flow rate to identify the influencing process parameters on weld bead geometry. Finite Element (FE) simulations are carried out using FE software SYSWELD considering the thermo-physical properties of the base material. A three-dimensional conical Gaussian heat source is employed for performing non-linear thermal analysis. The transient temperature profile and weld bead dimensions; depth of penetration and bead width are calculated by FE simulation. The simulated bead profile is compared with the experimentally measured profile and found to be very well correlated.

Influence of Beam Incidence Angle in Laser Welding of Austenitic Stainless Steel using Finite Element Analysis

This paper presents the influence of beam incidence angle on austenitic stainless steel sheet subjected to a high density laser beam having Gaussian power density distribution. Bead‐on trials are conducted on 3.15 mm thick commercial AISI 304 austenitic stainless steel sheet using a Nd:YAG laser source with a maximum output of 2kW in the continuous wave mode. The effects of beam incident angle on the weld bead geometry are studied using finite element analysis. Experiments are conducted with 600, 1000 and 1400W laser power and 800, 1400 and 2000mm/min welding speed. A three dimensional finite element model is developed for the simulation of non‐linear transient thermal analysis of the weld bead geometry for different beam incident angles using the finite element code ANSYS. The result reveals that by increasing the beam incident angle with constant beam power and welding speed, there is a considerable reduction in the depth of penetration‐to‐width ratio (d/w). Further, it is noticed that the process enters into conduction mode of welding from the keyhole mode of welding as the beam angle is increased beyond 10o. The comparison of the simulation results and the experimental data for weld bead geometry with different beam incident angles show good agreement.

Some studies on temperature field during plasma arc welding of thin titanium alloy sheets using parabolic Gaussian heat source model

In this paper, a new volumetric heat source model is developed for predicting the weld bead geometry during plasma arc welding of thin sheets of titanium alloy. Numerical simulations are carried out with the proposed parabolic Gaussian heat source (PGHS) model and already prevailing familiar heat source models namely, conical heat source and modified conical heat source, using finite element package COMSOL. The temperature-dependent material properties for Ti–6Al–4V alloy are considered for performing numerical calculations, which tend to influence the temperature fields while computing. Besides, the effect of trailing gas shielding, latent heat, and radiative and convective heat transfer are taken into account while performing the transient thermal analysis which significantly alters the sensitivity and accuracy of the model. Experimental trials on thin titanium alloy sheets are carried out to enable the validation of the proposed PGHS model. Subsequently, the outcome reveals that the PGHS model is capable and proved its high degree of efficiency in predicting the weld bead geometry more accurately than the existing heat source models. The distribution of heat intensity along the thickness of thin sheet is observed to be parabolic as predicted by the proposed model. The prediction appears to have a good correlation with the experimental result and it is clearly perceptible that the parabolic shape is more reliable and yields greater accuracy of the proposed heat source model.

Influence of Road Surfaces on Whole Body Vibration for Suspended Cabin Tractor Semitrailer Drivers

This paper presents a study on whole body vibration analysis for drivers of tractor semitrailers. The tractor semitrailer, namely, a suspended cabin tractor semitrailer was considered for the present investigation. The important process parameters such as different speeds, different road surfaces and different loaded conditions with driver seat interface acceleration in X- longitudinal, Y-transverse and Z-vertical axes were tested. The average running weighted root mean square accelerations obtained after conducting the experimental work were between 0.6265 and 1.5594 m/s2 at the driver seat interface in the translational axes. Based on the weighted acceleration the value was compared to ISO 2631–1:1997 to find the permitted exposure time of drivers. The acceleration suspended cabin tractor semi trailer drivers are exposed to exceeds the upper exposure limit for an 8-h work day as outlined in (ISO 2631–1:1997) [1] when they work continuously.

Mathematical modelling and optimisation of laser welding of butt joints

Laser welding is characterised by its high power density and concentrated heat input. The weld bead profile of laser welding depends on various parameters and these parameters are to be selected correctly to obtain the desired output. As the trial and error method for selecting weld parameters is very costly, suitable analytical methods has to be established for selecting optimum parameters for welding. In this paper the influence of laser welding parameters on the weld bead profile of butt joints are analysed and discussed. The experimentation is performed based on Box-Behnken design. Mathematical modelling is done to predict the responses and the adequacy of the model is tested using the analysis of variance. Numerical and graphical optimisation techniques are used to find the optimum process range which will improve the weld quality.

Numerical Studies on Heat Transfer and Fluid Flow during Laser Welding of Thin Sheet

Numerical simulation of heat transfer and fluid flow analysis of laser welding is essential to understand the physics of fluid motion, thermal cycles, heating and cooling rate and its effect on the formation of the final weld bead profile. The fusion geometry, weld thermal cycles, temperature and velocity field will vary depending on the welding process parameters. The influence of process parameters on the formation of weld bead geometry was analyzed in this study. In the simulation a plane Gaussian profile heat source was used to model the laser beam considering the equations of mass, momentum and energy. It was observed that due to the difference in surface tension coefficient the fluid moves from the central region of the molten pool to the outside. Increase in beam power or decrease in welding speed resulted in a high heating rate and less cooling rate due to high heat input. The simulated bead profiles were compared with the experimentally measured profile and was found to be in agreement.

Segmental vibration transmissibility of seated occupant from lumped parameter models

One of the important parameters for the comfort of a seated occupant of a vehicle is the dynamic parameter. The effects of vibration depend on biomechanical characteristics, transmissibility (TR) and apparent mass. The range of input vibration at the seat and TR at the driving frequency will decide the magnitude of the displacement at any point of the human occupant. The most preferred form of biomechanical model for unidirectional whole body vibration is the lumped parameter model. Lumped parameter models are formulated by number of masses depending on the number of degrees-of-freedom (d.f.). The objective of this work is to study the vibration TR by developing the equations of motion (EOM) for different d.f. models for the seated occupant. Then the generated equations of motion for lumped parameter models are solved using the frequency domain technique. In this paper two, four, seven and 11 d.f. models are considered. The TR values are determined by solving the derived parameters using the MATLAB program. The maximum seats to head TR in the case of two, four, seven and 11 d.f. are obtained at the frequency of 2 Hz, 2.5 Hz, 3.15 Hz, and 4 Hz respectively. The TR obtained from models is compared with real time experimental results. The comparison shows a better fit for the TR obtained from the four and seven d.f. models. There is a wide deviation from the TR observed with two and 11 degrees of models when compared with experimental results of the past literature.