Per Wennhage

Structural-acoustic Design of a Multi-functional Sandwich Panel in an Automotive Context

This article deals with the design and weight optimization of a multi-functional vehicle body panel in an automotive context. An existing vehicle design has provided functional design requirements regarding static, dynamic, and acoustic behavior of the components of a car roof. A novel, multifunctional panel is proposed which integrates the component requirements present in a traditional roof system within a single module. The acoustic properties of two configurations of the novel panel are examined using numerical methods including advanced poro-elastic modeling tools compatible with Nastran, and compared with numerical results of a finite element model of the existing construction.

Weight Minimization of Sandwich Panels with Acoustic and Mechanical Constraints

If a structure is carefully designed to fulfill acoustic as well as strength and stiffness requirements, the amount of additional damping materials can be kept to a minimum. In the present work a method to minimize the mass per unit area of a sandwich panel, taking into account both structural and acoustic requirements is presented. The sound reduction index for airborne sound is used as a constraint and the optimization is performed by mathematical programming methods. As an example a standard solution for sandwich plates is used to define maximum deflection and stresses as structural constraints.

Design and Implementation of an Experimental Research and Concept Demonstration Vehicle

This paper introduces the Research Concept Vehicle (RCV), an experimental research and demonstration vehicle developed at KTH Royal Institute of Technology. The vehicle is intended as a platform to implement, validate, and demonstrate research results from different research projects carried out at KTH. In its first generation, the RCV is a pure electric vehicle where each wheel is equipped with an in-wheel motor and individual steering and camber actuators. This high level of over actuation allows for a wide range of experimental evaluation in several fields of research, which is listed in this paper. Results from initial experimental test drives are also included.

Orthotropic Models of Corrugated Sheets in Finite Element Analysis

To reduce computational effort of finite element (FE) calculations a corrugated sheet is replaced with an orthotropic plate. Analytical expressions for the mechanical properties are studied and compared to finite Element calculations in extension, free vibration, and buckling. Good similarity is shown in the stiffened and transverse direction of the corrugated sheet; however, the orthotropic models do not give an accurate twisting behavior. The stiffened direction of the corrugated sheet best matches the analytical expressions. Keeping in mind the presented limitation, the orthotropic model presented herein can be used to drastically reduce the number of elements needed when modelling corrugated sheet with finite elements.

Weight Optimization of Large Scale Sandwich Structures with Acoustic and Mechanical Constraints

A generic model of it railway car body in sandwich design was weight optimized subject to various constraints. These constraints were global natural frequency constraints. buckling and wrinkling co ...

Weight optimization of sandwich panel with acoustic constraints, experimental verification

Weight optimization of a sandwich panel was performed. The constraints were both mechanical, in the form of stiffness and strength constraints, and acoustic, in the form of a required sound reduction index, R. The sound reduction index of the optimized panel and an initial configuration was measured under laboratory conditions and the results were compared to predicted values. Predictions and measurements of the sound reduction index were made in third-octave frequency bands. It was shown that the difference in R between the initial panel and the optimized one was predictable using the acoustic models and that the optimized panel fulfilled the constraints. The weighted average reduction index, RW, was also used to provide an engineering number for comparison.

Testing of Sandwich Panels Under Uniform Pressure

The properties of a testing device for transverse loading of simply supported sandwich panels using a uniformly distributed load are investigated. Differences between hard and soft simply supported boundary conditions are verified. Shear stream gages are used to measure the shear stress in the core of the sandwich. The deflection, strains on the upper face, and the load distribution and measured on an isotropic sandwich panel and the same properties are calculated using an analytical method and a finite-element method (FEM). The boundary conditions are investigated by letting the FEM program calculate the solution for both soft and hard simply supported boundaries. The results show that the type of simply supported boundary conditions has a considerable effect on the solution. It is shown that the test panel used in this research better represents the soft boundary conditions. It is noted that the pressure can vary substantially close to the corners of the panel but is uniformly distributed over the central part of the panel.

Optimisation of sandwich panels for the load carrying structure of high-speed rail vehicles

This paper investigates how various requirements, such as stiffness, strength, buckling, thickness and area density, influence the choice of load carrying sandwich panels for highspeed rail vehicle ...

Substitution of corrugated sheets in a railway vehicle's body structure by a multiple-requirement based selection process

To simplify construction, reduce weight and improve mechanical properties, a sandwich panel substitution process is performed on corrugated sheets in the floor and roof of a rail vehicle car body. A requirement based selection is used to design the sandwich panels with the corrugated sheet mechanical characteristics as boundaries. Car body stiffness is evaluated by modal analysis. The derived panels reduce the mass of the car body by 600–700 kg. Results show the varying importance of the longitudinal, transverse and shear properties of the floor and roof panels, as well as how efficient the corrugated sheets actually are.

Finite difference adaptation of the decomposition of layered composite structures on irregular grid

The finite difference method is used to solve the time-dependent thermo mechanical response of a layered composite structure subjected to fire. State variables of the composite are chosen whereby the external and internal boundary conditions are derived for an irregular grid through the thickness of the structure. The homogenised mass flux and specific heat capacity of pyrolysis gases over a layered composite is also defined. The formulations are tested against documented results found in the literature.