FEA Solver Java

A comprehensive Finite Element Analysis (FEA) solver library implemented in Java, supporting both 2D and 3D linear and nonlinear structural analysis.

Academic Project: This repository is part of a Master's degree project in Computational Engineering at Ruhr University Bochum (Ruhr-Universität Bochum), Germany.

📋 Features

• 2D Linear Elasticity Analysis - Planar stress and strain problems
• 3D Linear Elasticity Analysis - Solid mechanics with hex elements
• Nonlinear 3D Analysis - Advanced nonlinear material and geometric behaviors
• Truss Elements - Specialized 1D structural analysis
• Quad & Hex Elements - 4-node and 8-node elements for 2D/3D analysis
• Material Models - Linear elastic and custom material definitions
• Von Mises Stress - Built-in stress visualization and analysis
• Excel Integration - Read geometry and boundary conditions from Excel files
• 3D Visualization - Interactive visualization of structures and results
• GUI Support - Graphical interface for nonlinear analysis

📁 Project Structure

fea_solver_java/
├── src/
│   ├── core/                          # Base FEA library
│   │   ├── Element.java              # Base element class
│   │   ├── Node.java                 # Node definition
│   │   ├── Constraint.java           # Boundary conditions
│   │   ├── Force.java                # Load definitions
│   │   ├── Material.java             # Material properties
│   │   ├── Structure.java            # Main structure handler
│   │   ├── ElementQuad2D4N.java      # 2D quad element
│   │   ├── ElementQuad3D8N.java      # 3D hex element (8-node)
│   │   ├── LinearElastic2D.java      # 2D elasticity model
│   │   ├── LinearElastic3D.java      # 3D elasticity model
│   │   ├── VonMises2D.java           # 2D stress analysis
│   │   ├── VonMises3D.java           # 3D stress analysis
│   │   ├── Visualizer.java           # Result visualization
│   │   └── ReadGeometry.java         # File I/O utilities
│   │
│   ├── examples/                      # Practical implementations
│   │   ├── Linear2D/                 # 2D linear elasticity examples
│   │   ├── Linear3D/                 # 3D linear elasticity examples
│   │   ├── LinearTruss/              # 1D truss examples
│   │   └── Nonlinear3D/              # Nonlinear analysis examples
│   │
│   └── tests/                         # Test cases and validation
│       ├── Test3D/                   # 3D element tests
│       ├── TestCube.java             # Cube structure tests
│       ├── TestGeometry.java         # Geometry validation
│       └── TestString.java           # String tests
│
├── .gitignore                         # Git ignore rules
└── README.md                          # This file

🚀 Quick Start

Prerequisites

• Java 8 or higher
• Apache POI (for Excel file reading)
• JNUMERICS library (for matrix operations)
• INF.V3D library (for 3D visualization)

Basic Usage

Example: 2D Linear Analysis

import core.*;

Structure struct = new Structure();

// Create nodes
Node n1 = new Node(0, 0);
Node n2 = new Node(1, 0);
Node n3 = new Node(1, 1);
Node n4 = new Node(0, 1);

// Create element
ElementQuad elem = new ElementQuad(n1, n2, n3, n4);

// Define constraints and forces
Constraint c1 = new Constraint(true, true, true);   // Fixed
Force f1 = new Force(0, -1000, 0);                  // Load

// Add to structure
struct.addNode(n1);
// ... add more nodes and elements

// Solve
struct.enumerateDOFs();
struct.solve();

// Visualize
Viewer viewer = new Viewer();
Visualizer viz = new Visualizer(struct, viewer);
viz.drawElements();

Example: 3D Linear Analysis

import core.*;

// Create 3D hex element (8 nodes)
Node n1 = new Node(0, 0, 0);
Node n2 = new Node(1, 0, 0);
// ... define 8 nodes for hex element

ElementHex elem = new ElementHex(n1, n2, n3, n4, n5, n6, n7, n8);

// Similar workflow as 2D

🔍 Module Descriptions

Core Library (src/core/)

The foundation for all FEA operations:

• Element Classes: Base element definitions and derived types (Quad, Hex)
• Node & Constraint: Mesh definition and boundary conditions
• Material & Force: Material properties and load definitions
• Elasticity Models: LinearElastic2D and LinearElastic3D solvers
• Stress Analysis: Von Mises stress computation and visualization
• Structure: Main orchestration class managing assembly and solving

Examples (src/examples/)

Linear2D

2D planar stress/strain analysis with quad elements:

• Mesh generation from geometry files
• Linear elasticity solve
• Von Mises stress visualization

Linear3D

3D solid analysis with hex elements:

• 3D mesh handling
• Linear elasticity in 3D
• 3D stress visualization and export

LinearTruss

Specialized 1D truss element analysis:

• Truss structure definition
• Axial force analysis
• Small structure examples

Nonlinear3D

Advanced nonlinear analysis capabilities:

• Nonlinear material models
• Geometric nonlinearity
• Graphical user interface for parameter input
• Interactive visualization

Tests (src/tests/)

Validation and test cases:

• ElementTests: Verify element formulations
• GeometryTests: Mesh and boundary condition validation
• CubeTests: Common benchmark problems

📊 Analysis Types Supported

Feature	2D	3D	Nonlinear
Linear Elasticity	✅	✅	❌
Element Types	Quad	Hex	Hex
Material Models	Linear	Linear	Nonlinear
Visualization	✅	✅	✅
GUI Interface	❌	❌	✅

🛠️ External Dependencies

• JNUMERICS: Matrix and linear algebra operations
• Apache POI: Excel file reading for geometry input
• INF.V3D: 3D visualization engine
• ICEB.JNUMERICS: Numerical computing utilities

📖 Usage Examples

Reading Geometry from Excel

ReadGeometry reader = new ReadGeometry("geometry.xlsx");
reader.parseGeometry(struct);

Computing Von Mises Stress

VonMises3D vm = new VonMises3D(struct);
double stress = vm.computeStress(element);

Visualizing Results

Viewer viewer = new Viewer();
Visualizer viz = new Visualizer(struct, viewer);
viz.drawElements();
viz.drawConstraints();
viz.drawForces();

🔧 Development

Building

Compile using your preferred Java IDE or build tool:

javac -cp .:../lib/* src/core/*.java
javac -cp .:../lib/* src/examples/Linear2D/*.java

Running Tests

java -cp bin tests.Test3D.HexTest
java -cp bin tests.TestCube

Running Examples

java -cp bin examples.Linear2D.TestElement
java -cp bin examples.Linear3D.TestGeometry
java -cp bin examples.Nonlinear3D.GraphicalUI

📝 File Input Format

Excel Geometry Files

Expected columns:

• NodeID: Unique node identifier
• X, Y, Z: Coordinates
• ElementID: Element identifier
• Node1-8: Node references for element connectivity

🎯 Key Classes

Class	Purpose
Structure	Main analysis controller
Node	Point in space with degrees of freedom
Element	Base element (extended by specific types)
ElementQuad / ElementHex	2D/3D element implementations
Material	Material property definitions
Constraint	Boundary condition (fixed, free, etc.)
Force	Applied load
Visualizer	Results visualization
ReadGeometry	Input file parsing